ITIN: A Practical Step-by-Step Application Guide

If you will have tax obligations in the United States and do not qualify for a Social Security Number (SSN), the number you need to apply for with the IRS is called an ITIN. I see many founders get confused about this or apply too early when they do not need one. Here I will clarify everything: what it is, when you need it, and how to apply step by step under the current official rules.

What the ITIN Is and What It Is Used For

The ITIN (Individual Taxpayer Identification Number) is a tax identification number issued by the IRS to individuals who must file a tax return or report income in the United States and do not meet the requirements to obtain an SSN.

It has a strictly tax-related purpose. It is not a work permit, does not change your immigration status, and does not grant you Social Security benefits. It is also not the same as the EIN, which identifies your company as a legal entity rather than you as an individual.

Who Really Needs It

A practical rule that is always worth keeping in mind: you do not apply for an ITIN "just in case," but rather when a specific tax obligation requires it.

The most common cases among entrepreneurs and partners outside the United States are:

• Nonresident partners of a US company who must file or receive tax documents with the IRS.
• People who receive US-source income subject to withholding or who are required to file a federal tax return.
• Spouses or dependents who need to be included on a federal tax return.

How to Apply: Form W-7

The process is handled using Form W-7. As a general rule, the IRS requires you to submit this form with a valid federal income tax return that supports the application. The only exception is if you fall under one of the specific circumstances established by the IRS itself (for example, certain withholding situations or third-party information reporting).

Along with the W-7, you must prove your identity and foreign status. The IRS only accepts original documents or copies certified directly by the official issuing agency. Ordinary photocopies and notarized documents are not accepted and will cause your application to be rejected.

Ways to Submit It

The IRS currently provides two options: by mail or in person.

By Mail

You mail the complete physical package (Form W-7, the tax return if applicable, and the required documentation) to the IRS address. It is a straightforward option logistically, but the drawback is that you must part with your original identification documents if you do not have copies certified by the issuer.

In Person

If you prefer not to mail your original documents, there are in-person options:

• IRS Taxpayer Assistance Center: this is a free service where they review your W-7 and authenticate most documents.
• VITA sites: these are also free, although availability is limited and they operate only within the United States.
• Certifying Acceptance Agent (CAA): this is a paid authorized agent. They help you review and complete the W-7 and are authorized to authenticate most of your identification documents. Keep their limitations in mind: they cannot authenticate foreign military identification, and for dependents, they can only authenticate passports and birth certificates. Any document they cannot authenticate will have to be physically mailed with the application. There are CAAs both in the United States and in other countries.
• Acceptance Agent (AA): this is also a paid authorized agent who reviews and helps prepare the W-7, but the main difference compared with a CAA is that they do not authenticate documents. With an AA, you will still need to provide originals or copies certified by the issuing agency.

You can review the comparison between these options directly in the IRS table.

How Long the Process Takes

The IRS states that you should allow approximately 7 weeks to receive a notice about the status of your application. This timeframe increases to 9 to 11 weeks if you file during peak tax season (January 15 through April 30) or if you submit the application from outside the United States.

Keep in mind that these timeframes are IRS estimates for informational purposes, not guaranteed dates. No one—neither we at Maera nor any outside agent—can promise you an exact issuance date or guarantee the approval of your ITIN.

Common Mistakes That Delay the Process

I see applications stalled because of simple oversights that are easy to avoid:

• Submitting Form W-7 without attaching the federal tax return when no exception applies to you.
• Attaching ordinary photocopies instead of original documents or copies certified by the issuing agency.
• Differences between how your name appears on your passport and on the rest of the documents.
• Leaving fields incomplete in the section where you explain the tax reason for requesting the ITIN.

How This Fits Into Your Operations

When setting up your business in the United States, the order of the steps matters. First, it is helpful to understand what an LLC is and how it is taxed so you have a clear grasp of your tax fundamentals. Then you obtain your company's number by understanding what the EIN is and how to apply for it from outside the United States, or the specific steps if you are handling your EIN from Mexico: how to apply with the IRS. Only then, if your personal situation requires it for tax purposes, do you move forward with the ITIN.

Keeping this structure in order will make it easier for you to later meet obligations such as Form 5472 for a foreign-owned LLC: a practical guide and determine with banks or clients which form applies to you among W-8BEN, W-8BEN-E, or W-9: which one a foreign LLC owner needs.

If you need support setting up or keeping your company in good standing, you can review our plans. Keep our legal notice in mind: at Maera, we are an administrative service, and we help you with operational and document management. We are not a law firm or an accounting firm, and this information is general in nature and does not constitute legal or tax advice. Always review the official guidelines and consult a professional if your specific case warrants it.